There are many types of cargo containers. There are cargo containers designed to be loaded onto ocean going ships. There are cargo containers specially shaped to fit into the curved hulls of airplanes. There are cargo containers that are transported by train. Cargo containers are often transported as trailers by trucks.
There are several problems associated with cargo containers. One problem is that the rectangular shape of the container creates drag that hinders the transport of the container. It is desirable to have an aerodynamic cargo container that reduces drag.
A drag force acts on an object which moves in a fluid environment such as air or water. This drag force includes several specific drag forces wherein the main one is known as a pressure drag force. The pressure drag force is caused by a net pressure force acting on the object. The rear end contribution to the pressure drag is called “base drag”. Flow separation at the base of the moving object creates a vortex system and reduces base pressure thus increasing drag. This problem exists for truncated objects, which have blunt bases, such as a box, a cylinder and the like. Drag forces on the trailer reduce the fuel efficiency of the truck pulling the trailer, and increase the cost of transporting the cargo container. It is desirable to reduce the cost in transporting a cargo container.
Another problem is that automobiles often crash into the rear of trailers causing injury to the automobile and passengers. It is desirable to have a trailer that is designed to reduce the damage caused to automobiles and passengers that crash into the rear of a trailer.
Another problem is that cargo containers pulled by trucks must often be moved into close proximity to a loading dock so that the cargo can be loaded or unloaded. The hinged doors of a cargo container can limit how close a cargo container can be positioned to a loading dock. It is desirable to have a cargo container that can be opened while in close proximity to a loading dock.
There have been attempts to solve some of these problems. For example, U.S. Pat. No. 6,286,894 that issued to Kingham teaches a transportable hauling container, such as a trailer of a tractor-trailer combination, has a rear portion that is configured in or convertible to a wedge shape. Movable portions are located at the rear sides of the trailer that can pivot inward toward a longitudinal centerline. Movable flaps also are located at the rear top of the trailer, which can pivot downward in alignment with the movable portions. The movable portions and flaps can be secured relative to each other in various combinations, thereby providing a more aerodynamic configuration of the trailer rear end. The container or trailer can be configured in such an arrangement, or be convertible from a standard configuration which also includes doors at the rear of the trailer, to a more aerodynamic configuration. A method is also disclosed, which includes operations for converting such a convertible trailer between the standard and aerodynamic configurations.
For example, U.S. Pat. No. 4,924,780 that issued to Hart teaches a rail car enclosure having a bottom deck, sidewalls and a curved roof defined by at least one slope on each side connecting a flat top of the roof with the sidewalls and the deck connecting the opposite end of each sidewall to form an open end of the rail car. At least one intermediate deck extending between and connecting the sidewalls. An upper track mounted on the uppermost intermediate deck and a bottom track mounted on the bottom deck such that the upper track and bottom track curve around the sidewalls of the rail car. A plurality of panels hinged together at the marginal edges thereof to form a left and right door to slide on the upper and bottom curved tracks between a closed and stowed position. The doors parallel to the exterior of the sidewalls in the stowed position and standing substantially in one plane to fill the open end of the rail car in the closed position.
U.S. Pat. No. 4,236,745 that issued to Davis teaches a truck body streamlining device, and more specifically to a collapsible, pivoted rear door attachment which when deployed in its operative position forms a reduced air drag surface on the rear of the truck body to minimize the wind resistance of the vortex which normally forms at the rear of a square backed truck.
U.S. Pat. No. 4,077,330 that issued to Peisner teaches an end closure for a rail car which comprises a pair of sliding doors mounted for movement between open and closed positions. One of the doors has a recess to clear a brake lever when the door is open. A panel is provided to close the recess when the door is closed. The panel is automatically moved to a position opening the recess when the door is opened and automatically moved to a position closing the recess when the door is closed.
U.S. Pat. No. 3,995,563 that issued to Blunden teaches an end closure for a rail car which comprises a pair of sliding doors. Locking mechanisms provided for securing the doors in closed position extending across the end of the rail car as well as in open and in intermediate positions. Each door moves from closed to open position through an opening in the side wall of the rail car to an open space on the outer side of the side wall within the allowed rail car clearance.
Thus, it is desirable to provide a cargo container with an improved aerodynamic design, doors that can be operated while the container is in close proximity to a loading dock, and a rear skirt that attenuates the damage caused to automobiles that crash into the rear of the container.